Volatile organic compounds (VOCs) are a kind of air pollutant similarly dangerous to particulate matters. As indicated in relevant studies, VOCs with a concentration of up to 0.2-0.3 mg/m3 may result in such discomfort symptoms as irritation to human body; whereas VOCs with a concentration up to 3-25 mg/m3 may result in such symptoms as irritation and headache; VOCs with a concentration over 25 mg/m3 may result in extremely obvious toxic effect to the human body. Furthermore, VOCs may also incur such secondary pollution as photo-chemical smog in addition to its inherent hazards.
Most of the industrial exhaust gases containing VOCs are from industries that take coal, petroleum and natural gas as the sources for organic compounds or relevant chemical industries; wherein, alcohols and aldehyde are extensively used as industrial solvents, thus generating large amounts of discharge. In view of the present status of industrial VOCs exhaust gases of low concentration and large quantity, biological purification technology is a relatively ideal treatment approach. However, for such VOCs as isopropanol and ethanal, the effect of biological treatment is unsatisfactory. In recent years, researchers have tried to solve the problem of decomposition of VOCs by selecting microorganisms with high efficiency.
Bacillus pallidus ST3, an isopropanol degrading bacteria as selected by Bustard and his colleagues, is available for degrading 24 g/L isopropanol under the temperature of 60° C. McEvoy and his colleagues discovered Chlorella vulgaris which is effective for degrading of isopropanol of high concentration with specific growth rate for degrading 2-16 g/L isopropanol up to 0.0017-0.0038 h−1. Mohammad and his colleagues have successfully separated Sphingobacterium mizutae ST2, a strain for degrading isopropanol with maximum specific growth rate and maximum specific degrading rate (concentration of isopropanol is 7.5 g/L) up to 0.0045 h−1 and 0.045 gram/(gram×hour) respectively.
In addition to such VOCs as alcohols and aldehyde, effluvial organic sulfides, such as sulfoether and mercaptan compounds, have higher requirements for pollution control due to low olfactory coefficient. With regard to demethyl sulphide and dimethyl disulphide, degrading bacteria reported includes Hyphomicrobia sp. EG, Thiobacilli sp. ASN-1, Pseudomonas acidovorans and Methanogens sp. MPT4; wherein, specific growth rate of Thiobacillus sp. ASN-1, Hyphomicrobium sp. EG and Methanosarcina MPT4 is up to 0.10 h−1, a0.08 h−1 and 0.01 h−1 respectively.
Chinese Patent Publication No. CN 103667119 A has disclosed a strain for degrading ethyl mercaptan as well as its culture method and application. Such strain is named as Pseudomonas sp. WL2 preserved at China General Microbiological Culture Collection Center (CGMCC) on Jul. 8, 2013 with the deposit number of CGMCC NO. 7898. Such strain belongs to aerobic gram-negative bacteria, which can grow by taking ethyl mercaptan as the sole carbon source and energy and thoroughly transform them into CO2 and H2O through mineralization. Under pure culture conditions, such strain is capable of degrading ethyl mercaptan at the temperature of 25˜30° C. and pH value of 6˜8. Such strain features in excellent substrate accommodation and universality, which can also be used for degrading propanethiol and methanol; however, its substrate tolerance and universality are not so satisfactory.